Featured image not showing on homepage but showing on post page

I am currently trying to help a company to develop their website(This website was developed previously by a company. I have the source code, but they refuse to help me on anything:( ). I uploaded a new post yesterday, everything goes fine except the featured image that i uploaded in the post section did not show up on my blog page. Here are something i have tried: 1. I resized the image to the previous post’s featured images, but nothing happened.2. I downloaded previous featured images(which display perfectly on the previous posts), then i uploaded the exact same image, and it still doesn’t work with the re-uploaded image. However, the images that was saved in the media already (for the previous posts) could work perfectly on my new post. How do i solve this problem?